Problem: If $a + b + c = -1$ and $x + y = 7$, what is $-9a - 7x - 9c - 9b - 7y$ ?
$= -9a - 9b - 9c - 7x - 7y$ $= (-9) \cdot (a + b + c) + (-7) \cdot (x + y)$ $= (-9) \cdot (-1) + (-7) \cdot (7)$ $= 9 - 49$ $= -40$